The Alpha Magnetic Spectrometer’s Final Endeavour (Updated)

Carl discusses the long and bumpy journey as well as the scientific goals of the Alpha Magnetic Spectrometer, due to be ferried to the ISS at the end of April on the final flight of the Space Shuttle Endeavour…

NASA recently announced that the final flight of the Space Shuttle Endeavour is scheduled for April 29th 2011. Whilst this launch marks the final flight of Endeavour and the penultimate launch before the retirement of the entire fleet, it also marks the installation of a project that has been waiting for a ride to the International Space Station (ISS) for over 10 years. The Alpha Magnetic Spectrometer (AMS) will be strapped into Endeavour’s cargo bay next week to make the bumpy journey to the ISS where it will be fixed on the outside and conduct a search for anti-matter, dark matter and cosmic rays.

The Alpha Magnetic Spectrometer

The AMS is the first large magnetic spectrometer to be used in space. Both AMS-01 and AMS-02 will use a massive permanent magnet to alter the paths of charged particles that will subsequently be detected by a series of instruments within the experiment. It will be able to separate matter from anti-matter, determine the sign of the charge of a particle and measure the energy of incoming particles and cosmic rays.

The AMS was proposed back in 1995, when ideas like dark matter and dark energy were starting to gain some momentum and when humans were starting to build large, permanent outposts in orbit around the Earth where experiments such as this could be staged. A prototype was built, called AMS-01, and flown on board the Space Shuttle Discovery in 1998. During this mission, it placed an upper limit on the ratio of anti-helium to helium of ~10^-6 and proved the detector worked in space.

After the success of AMS-01, the development of the full system was started. Dubbed AMS-02, it was to begin what has been a long and bumpy journey to the launchpad. During the development of AMS-02, the tragic loss of all seven crew on board the Space Shuttle Columbia during re-entry in 2003 cast the project into doubt as to whether it would ever leave the ground. For 29 months after the disaster, the Shuttle fleet were grounded and AMS-02 unable to get to the ISS. More delays and scheduling issues blighted the project until former President George W. Bush scheduled in one extra Shuttle flight before their retirement, on which AMS-02 will be launched on.

Scientific Goals

The AMS will help investigate why our universe appears to have favoured matter over anti-matter. Everything around us is observed be be made of matter and we don’t observe anti-matter in our universe. Why is this the case if the same amount of matter and anti-matter were created during the Big Bang? This asymmetry is something AMS will help investigate. The observation of just one anti-helium nucleus would provide evidence for large amounts of anti-matter elsewhere in the universe and drastically alter our cosmological models of the universe’s origins.

Dark matter is supposed to account for about a quarter (~23%) of the ‘stuff’ in our universe with dark energy accounting for nearly three quarters (~72%) and the normal matter around ~5%. AMS will search for dark matter candidate particles by looking for an excess of charged and neutral particles in its detections. If this happened, it would increase support for supersymmetry and a dark matter candidate known as the neutralino.

Another asymmetry is the observation that all matter on Earth is made of just two quarks; the up and down quark. Six types of quark have all been experimentally observed (read a previous post on quarks), so why is most matter only made of two? The AMS will try and detect matter that is made up of three quarks – up, down and strange. These sort of particle are known as strangelets, are dark matter candidates and would be a totally new form of matter, if detected.

You may already be thinking how much more can this piece of equipment do, but it has one final job to do. AMS will also study the origin and interstellar behaviour of cosmic rays on a long-term scale. This sort of study is vital for planning interplanetary missions between, for example, Earth and Mars. Cosmic radiation presents a significant obstacle to future manned space flight due to their harmful effects on humans. Knowing how many cosmic rays they’re likely to encounter means that shielding can be designed to protect them.

Whilst the AMS has had a longer than normal journey to the launchpad, it has an equally long journey ahead of it. Once attached to the outside of the ISS, the project will run continuously for 10 years, or even more if the life of the ISS is extended. The results of this experiment will provide the tightest constraints on the models we use to explain our universe, the particles in it and their origins.

The Final Endeavour

The second to last ever flight of a Space Shuttle will occur with the launch of the AMS. Last week, NASA announced the post-retirement homes of the remaining Shuttle’s with Endeavour looking at spending its days in the California Science Center in Los Angeles. Mark the date in your diary: 29th April 2011, 19:47 UTC.

Further Your Knowledge

Cosmology and particle physics are exciting and rapidly developing areas of research. Theories are constantly being put to the test by experiments such as this. Do some research on the following topics to quench your thirst for all things physics!

• Supersymmetry
• Dark matter candidates
• Cosmic rays
• AMS-01 (prototype AMS, flown in 1998)

Header image credit: AMS-02 Collaboration
Image credits: NASA / WMAP Science Team, Michele Famiglietti, AMS-02 Collaboration